The present invention refers to a reinforced concrete pile of the type having a collar or similar fitting at least at one of its end, to which axially running reinforcing bars are attached. The invention also refers to a method of manufacturing such piles, as well as to the collar provided at the pile.
The collars fitted at one or both ends of a concrete pile, may be shaped as points, shoes or joint elements, and must be attached to the pile in such a manner that they can also take care of tensile strain loads in the pile. Hitherto the attaching of the collar has usually been made by means of anchor bolts, threaded into the collar and arranged parallel to the axial reinforcing bars in the pile. The anchor bolts usually have length of about one meter, and as many bolts as axial reinforcing bars are provided, fitted intermediate the ends thereof. Hereby a rather tight basket structure is obtained, which makes the introduction of the concrete compound at the ends of the pile difficult. When such a pile is subjected to tensile strain the axial forces cannot be transferred directly from the reinforcing bars to the collar, but must pass over to the anchor bolts by way of the concrete. This is not well suited for such action, so the actual transfer capacity is limited. Similarly the power strokes, when driving the pile, will largely have to be transferred from the anchor bolts to the reinforcing bars by way of the concrete.
It has been proposed to weld the axial reinforcing bars to the collar, but on the one end such welding will not provide the necessary strength, and on the other hand the collar is often made of nodular cast iron and the reinforcing bars of high class steel, so a welding will be generally difficult.
For a long time a desire to attach the reinforcing bars directly to the collar has been felt, but no simple, reliable solution has been found.